title: The dose-response relationship between in-ear occupational noise exposure and hearing loss.
abstract: OBJECTIVE
  Current understanding of the dose-response relationship between occupational noise and hearing loss is based on cross-sectional studies prior to the widespread use of hearing protection, and with limited data regarding noise exposures below 85 dBA. We report on the hearing loss experience of a unique cohort of industrial workers, with daily monitoring of noise inside of hearing protection devices.
  
  
  METHODS
  At an industrial facility, workers exhibiting accelerated hearing loss were enrolled in a mandatory programme to monitor daily noise exposures inside of hearing protection. We compared these noise measurements (as time-weighted LAVG) to interval rates of high-frequency hearing loss over a 6-year period using a mixed-effects model, adjusting for potential confounders.
  
  
  RESULTS
  Workers' high-frequency hearing levels at study inception averaged more than 40 dB Hearing threshold level (HTL). Most noise exposures were less than 85 dBA (mean LAVG 76 dBA, IQR 74-80 dBA). We found no statistical relationship between LAvg and high-frequency hearing loss (p=0.53). Using a metric for monthly maximum noise exposure did not improve model fit.
  
  
  CONCLUSIONS
  At-ear noise exposures below 85 dBA did not show an association with risk of high-frequency hearing loss among workers with substantial past noise exposure and hearing loss at baseline. Therefore, effective noise control to below 85 dBA may lead to significant reduction in occupational hearing loss risk in such individuals. Further research is needed on the dose-response relationship of noise and hearing loss in individuals with normal hearing and little prior noise exposure.
authors.affiliation: Occupational and Environmental Medicine Program, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Rabinowitz
authors.forename: Deron
authors.initials: D
authors.lastname: Galusha
authors.forename: Christine
authors.initials: C
authors.lastname: Dixon-Ernst
authors.forename: Jane E
authors.initials: JE
authors.lastname: Clougherty
authors.forename: Richard L
authors.initials: RL
authors.lastname: Neitzel
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004423:Ear; D004430:Ear Protective Devices; D004784:Environmental Monitoring; D005260:Female; D006309:Hearing; D006316:Hearing Loss, High-Frequency / Q000209:etiology*; D006317:Hearing Loss, Noise-Induced / Q000209:etiology*; D006801:Humans; D007221:Industry; D008297:Male; D008875:Middle Aged; D009623:Noise, Occupational / Q000009:adverse effects*; D009784:Occupational Diseases / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations; D012307:Risk Factors; D014937:Work
keywords: Dose response; Hearing loss; Noise induced